Chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) compounds have been used as refrigerants, fire extinguishing agents, propellants, and solvents since the early twentieth century. However, CFC and HCFC compounds are now believed to deplete the ozone layer of the earth via UV-promoted reactions. As a result, the U.S. Environmental Protection Agency has already banned the production and importation of certain products comprising CFC and HCFC compounds.
Internationally, the Montreal Protocol has set out plans for replacing CFC and HCFC compounds with hydrofluorocarbon (HFC) compounds. However, the cost of producing HFC compounds is considerably higher than that of producing CFC or HCFC compounds. Presently, industrial fluorination processes for producing HFC are based on hydrogen fluoride (HF) fluorination of chlorocarbons. FIG. 1 presents examples of known potential multistep routes to produce 1,1,2,2,2-pentafluoroethane (HFC-125) and 1,2,2,2-tetrafluoroethane (HFC-134a).
As illustrated in FIG. 1, multistep processes are typically required to produce HFC-125 from either 1,1,2-trichloroethene (triclene) or 1,1,2,2-tetrachloroethene (perclene). For example, HFC-125 can be produced by first converting either triclene or perclene into 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123) and then fluorinating HCFC-123 to 2-chloro-1,1,1,2-tetrafluoroethane (HCFC-124). HFC-125 can then be produced by performing chlorine-fluorine exchange on HCFC-124 with hydrogen fluoride. Similarly, as illustrated in FIG. 1, HFC-134a can also be produced with either triclene or perclene using multistep processes.
The processes for producing HFC-125 and HFC-134a are more complex, both chemically and operationally, than those for CFC and HCFC compounds. Moreover, both the triclene and perclene-based processes require disposing of hydrogen chloride (HCl) byproducts. Procedures and equipment are available to convert some of the HCl byproducts into a chlorine (Cl2) gas and subsequently recycle the chlorine gas back into the production process. Nonetheless, this recycling operation adds to the cost of the overall HFC production process. Therefore, there is a need to develop more efficient and cost-effective processes for producing HFC compounds, such as HFC-125 and HFC-134a.